The invention relates to a backpack for holding and transporting papers, books, school supplies, etc., which includes a gusset for expanding the interior volume of the backpack. More particularly, the backpack of the present invention includes an expandable gusset which is sewn into the lining of the backpack and which has a zipper attached around a periphery thereof. The zipper is provided so that the backpack may be modified from a "compact," gusset folded configuration to an expanded, gusset unfolded configuration simply and easily. In particular, the zipper for the gusset of the present invention is generally kept in the "compact," gusset folded configuration. However, when additional storage volume is required, the zipper may be unzipped to allow the gusset to unfold, thereby expanding the interior volume of the backpack. Preferably, a support flap is provided for the base of the backpack which folds down over the floor panel to provide additional support for the backpack base. Additionally, in a preferred embodiment, the zippered gusset of the present invention is positioned on the back portion of the backpack and extends approximately three fourths of the height of the backpack in order to prevent an undue amount of stress from being placed on the seams of the gusset or the gusset itself.
In the past there have been backpacks and knapsacks of many sizes and shapes which are designed for use by school-aged children for carrying textbooks, notebooks, pens, pencils and other school supplies to and from classes, as well as back and forth between home and school. While these backpacks have varied in shape and design, they generally have been constructed in a similar, rather conventional manner. For example, a standard backpack has generally included two shoulder straps, a main compartment which is enclosed by a zipper and at least one additional auxiliary compartment or pouch, for storing smaller items. An example of a backpack that is similar to this "standard" backpack is disclosed in U.S. Pat. No. 4,085,873 to Schweitzer. Notwithstanding the extra pouch provided on the Schweitzer backpack to allow the backpack to be collapsed inward to form a streamlined pouch when the backpack is not in use, the rest of the features (two shoulder straps, a zippered central compartment, etc.) of the Schweitzer patent are fairly standard to typical school use backpacks and are known in the industry.
While backpacks similar to the one disclosed in Schweitzer have generally adequately fulfilled students' transportation and storage requirements to date, there recently has been a need to have backpacks which have larger storage capacities than prior art backpacks. In particular, with larger textbooks, a greater emphasis on homework assignments, and in some instances, the complete elimination of school lockers, the need for larger capacity backpacks has become attenuated. Accordingly, there have been several attempts to provide improved backpacks which address this need. For example, U.S. Pat. No. 5,743,447 to McDermott discloses a portable variable capacity backpack having detachable shoulder straps, wheels, a handle, at least one detachable compartment, and an expandable compartment for storing books and school supplies. U.S. Pat. No. 5,797,529 to Lavine discloses a convertible multi-use bag which may be converted from a backpack, to a tote bag, to a fanny pack. The bag of the Lavine patent is characterized in that it may be simply and easily converted between the above-identified configurations in a way which does not require the "stuffing" of a larger pocket into a smaller one.
Additionally, the use of gussets to increase the volume of storage bags other than backpacks is known. For example, U.S. Pat. No. 2,173,120 discloses a portable storage bag which uses an expandable gusset having front and rear flexible panels, preferably made of leather, that are spaced apart by a split flexible gusset having a zipper mechanism for closing the gusset. A strengthening member is employed to help the flexible components and gusset to retain their desired shape. A soft sided leather briefcase made by W.K. Leathers which utilizes a gusset which may be zippered shut when not in use is also known. The gusset of the W.K. Leathers briefcase is used to expand the storage volume of an exterior pocket of the briefcase when the zipper is opened. However, the gusset of the W.K. Leathers briefcase extends around the entire perimeter of the storage pocket, meaning that the weight of the contents of the briefcase must be borne by the seams of the gusset.
While many of these prior art backpacks and storage bags have advantages, there continues to be a need to design a backpack which has the attributes and styling of a conventional school use backpack but which has the capability of expanding when a larger storage volume is required. Additionally, while it is important for current school-use backpacks to fulfill the requirements of greater storage capacity and ease of use, it is almost equally important for these backpacks to have design attributes which are attractive and look "cool" to the consumers of the backpack. Additionally, the durability of the backpack is a significant concern given the weight of the textbooks that are carried in the backpack and the abuse that is generally given to the backpack by its user.